Patent GB-931997-A (GB)
Title: Improvements in or relating to nuclear reactors
IPC: G21C3/04
Filed: 1961-12-05
Abstract: 931,997. Nuclear reactors. GENERAL DYNAMICS CORPORATION. Dec. 5, 1961 [Dec. 7, 1960], No. 43576/61. Class 39 (4). The fuel elements 22 of a high temperature gas - cooled reactor are arranged in clusters which are supported by means of hangers 60 secured at their upper ends to supporting boxes 52 between graphite separator plates 32 providing a honeycomb arrangement within the reactor core. Each box 52 carries supporting flanges 54 which rest upon the upper surface of the top grid plate 40 of the reactor core, and an upwardly-projecting part 66 which is adapted to be grasped by a fuel-handling mechanism 24. Each fuel element 22 (Fig. 5), comprises an elongated outer sleeve 41 of impervious graphite threadedly engaged at its lower end with a tapered graphite section 42 forming a portion of the bottom reflector of the core. The upper end of the sleeve 41 is threadedly engaged with a porous graphite sleeve portion 43 connected at its upper end with a hanger 60. Located within the outer sleeve 41 is an inner container 44, also of graphite, enclosing a plurality of vertically stacked fuel compacts 46 with a block 45 of moderator material disposed adjacent each end of the stacked fuel compacts 46. Coolant gas, e.g. helium, enters the reactor pressure vessel 12 through an inlet 14 and is directed upwardly along the side walls 18 of the vessel by thermal shield walls 20 and then downwardly through the reactor core, entering the fuel elements 22 through the porous sleeve portions 43 and then passing down between the inner container 44 and the outer sleeve 41 along grooves 47 in the surface of the former to a position below the fuel compacts 46 before passing up along grooves 48 in the surface of the fuel compacts 46 and the moderating blocks 45. The coolant then passes through an initial fission products trap 49 to an axial passageway 51 which communicates with the axial bore 75 of the hanger 60. Passages 72 in the base 58 of the supporting box 52 connect the axial bores 75 with passages 76, 78 and 80 in the walls of the box and a passage 84 in the top grid plate 40. The latter, along with other passages 84, communicates with fission products tanks 70 around the upper wall of the pressure vessel 12. Coolant gas leaves the pressure vessel 12 through an outlet 16 coaxial with the inlet 14. The upper portion of the vessel 12 is additionally cooled by means of a conduit 28 connected with the source of coolant (not shown) and including a section 30 extending around the inner wall of the vessel. The reactor core is provided with shielding material around the sides and bottom, the graphite separator plates 32 being supported at their lower edges by graphite columns 34 which rest on a continuous graphite base 36, supported in turn by a structural steel base 38 at the bottom of the vessel 12. The elements 22 of each cluster are secured together adjacent their lower ends by graphite keys 68 which extend through aligned openings in the bottom reflector extension portions 42. The grid plate 40 provides the shield between the top part of the vessel 12 and the core.